media: atomisp: cleanup ia_css_isp_configs() code

The auto-generated code inside ia_css_isp_configs() is more
complex than it should be. Also, it doesn't return any errors.

However, the functions called by it can mis-configure the pipelines,
but, as there's no way to return errors, it internally calls the
assert() macro.

So, add a return parameter to each routine there, in order to
prepare the code to be more robust.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>